I read htat you have a 1.5 G tank. I think you should upgrade to a 2.5 or a 5 at least. At petco, they're having a sale on that. I got my 5.5 for $15. I could've gotten a 2.5 for $13 and a 10G for $15 as well. But look at this coupon page. scroll down till you see a green and white rectangle. http://www.petco.com/petco_Page_PC_p..._Nav_1347.aspx
$1 per 1 Gallon of tank. smallest tank though is 10G. And you ahve to be a petco PALS member. But remember, bigger tank = more swimming room for fish/happier fish. But make sure that your filter can filter all the water (made for that amount of gallons).
As for food heres direct quote from a more "experienced" member of this site to me:
"And as far as feeding the betta goes, I suggest getting a high quality betta pellet like OmegaOne betta buffet pellets, Atison's betta pellets, Ken's Betta Crumbles, or New Life Spectrum. These are all good brands. If you cannot find these particular ones, look in the ingredients--meat should be the first ingredient, preferably "whole" meat, like whole salmon, whole krill, whole fish meal--stuff like that. If you see "wheat" or "flour" anything before the meat--put it back, it's garbage. If you see MSG or copper sulfate in it, it's also garbage--put it back. I usually feed my fish 3 pre-soaked pellets a day--soaking them in tank water helps prevent bloating. 2 pellets twice a day is also a good idea if you have time for that.
Avoid freeze-dried foods, they are not good nutritionally, and they cause some of the worst constipation in fish I have ever seen. They're terrible. Frozen foods like hikari's spirulina brine shrimp and blood worms are a good treat, I usually use frozen foods twice a week. It's good to vary the diet with different pellets and frozen foods because no single pellet formula can provide your fish with complete nutrition.
In this hobby you learn very quickly that any product with a big picture of a betta on it is only intended to catch your eye and trick you into thinking it's a good product for a betta. It isn't. Don't be fooled and don't let the pet store people make you think that bettas come from tiny mud puddles and can live at room temperature or any of that other nonsense." - Adastra
Very good advice^